Seldom opposite (5)

I believe the answer is:

often

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'seldom' is the definition.
Both the answer and definition are adverbs. Maybe you can see an association between them that I don't see?

I cannot understand how the remainder of the clue works.

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(Other definitions for often that I've seen before include "Frequently, habitually" , "Repeatedly with regularity" , "Quite frequently" , "on many occasions" , "Regularly" .)

I've seen this clue in The Globe and Mail.

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